functional dependencies candidate keys

Question

Consider the following relation and the set of functional dependencies (FDs). R = (A B C D E F G H I)

D -> H
DH -> A
EFH -> C
AF -> IG
CD -> ABG
IB -> C
G -> I
IBC->E
F -> H
C -> IE 

1. Find the candidate key(s) of R.
2. Find the minimal cover of FD set.

I think "DF" is one of candicate keys.

Answer 1

The ONLY candidate key is DF.

And the Minimal cover is as follows:

D->AH;
EF->C;
AF->G;
CD->ABG;
IB->C;
G->I;
F->H;
C->IE